ci: fix array iteration, variable leaks, and spurious full-reactor lint runs

[lqiu96]

Summary

Fixes several correctness bugs and edge cases in Kokoro CI build and helper scripts:

1. Fix Array Iteration in update_all_poms_dependency (.kokoro/common.sh):

   • for pom in $POMS; do only iterated over the first element of the array.
   • Updated to for pom in "${POMS[@]}"; do.
   • In find_all_poms_with_versioned_dependency, reset POMS=(), scoped local arrays, and pre-filtered candidate files with grep -rl "<artifactId>${1}</artifactId>" --include="pom.xml" . before running xmllint.

2. Fix Variable Leaks in generate_graalvm_modules_list (.kokoro/common.sh):

   • Fixed typo where modules_assigned_list+=("${module}") appended a leaked ${module} variable instead of the loop variable ${maven_module}.

3. Prevent Spurious Full-Reactor Lint Scans (.kokoro/build.sh):

   • When only excluded files (such as samples or benchmarks) were modified, has_code_change="true" was set, but changed_modules was empty after exclusions.
   • This left MODULE_FILTER="", causing Maven to run format/checkstyle without -pl across the entire 280+ module reactor.
   • If changed_modules is empty after exclusions, cleanly exit 0 and skip linting.

Verification

• bash -n .kokoro/common.sh .kokoro/build.sh
• git diff --check
• bash .kokoro/common_test.sh

[gemini-code-assist]

Code Review

This pull request optimizes and fixes issues in the Kokoro build scripts. Specifically, it skips the linter check early in .kokoro/build.sh if no relevant Java modules are affected, fixes a module assignment bug in .kokoro/common.sh, and optimizes the POM file search by using grep instead of find. The review feedback suggests making the grep pattern in find_all_poms_with_versioned_dependency more robust by allowing optional whitespace around the artifact ID to prevent silently skipping files with non-standard formatting.